Organic-inorganic hybrid materials are such materials that are able to exhibit both properties of an organic material and properties of an inorganic material by binding the organic material with the inorganic material based on a physical or chemical method.
The method that has been used the most to prepare the organic-inorganic hybrid thin film is the sol-gel method and it enables the easy preparation of organic-inorganic hybrid materials at low temperatures with the result that research thereon has been carried out extensively for a long time. Nevertheless, the sol-gel method has shortcomings such that it is difficult to control in terms of a monomolecular layer and that deformation occurs following thermal treatment, which makes it difficult to prepare an organic-inorganic hybrid thin film of high quality.
Another method for preparing the organic-inorganic hybrid thin film is based on intercalation and enables the preparation of the organic-inorganic hybrid material which was difficult to prepare by the sol-gel method. Nevertheless, because this method is also difficult to control in terms of a monomolecular layer and has slow deposition rates, it presents difficulties when preparing an organic-inorganic nano hybrid super-lattice of high quality.
The molecular self-assembly method prepares an organic-inorganic hybrid thin film by using static electricity and is a very useful method that enables polymer, nanoparticles, nanoplate, etc. to be grown in a layer form. Much effort is being spent on researching it. Nevertheless, the molecular self-assembly method prepares organic-inorganic hybrid thin films by using static electricity and does not represent technology that controls a monomolecular layer in a strict sense. Its low thermal stability makes it difficult to prepare a stable organic-inorganic hybrid thin film of high quality. In addition, the thermal deposition (evaporation) method prepares an organic-inorganic hybrid thin film in a gas phase and makes it difficult to control a monomolecular layer. In addition, its raw material molecules are very restricted so that its applications are also limited.
In order to solve such problems with the existing methods for preparing an organic-inorganic hybrid thin film, molecular layer deposition technology has been developed that enables not only organic polymers but also organic-inorganic hybrid materials to be deposited. The molecular layer deposition technology represents gas phase deposition in which inorganic or organic molecules can be controlled in a molecular unit based on the self-controlled surface reaction of inorganic or organic molecules. The S. M. George group as a representative example used the molecular layer deposition technology to prepare the alucone polymer film with trimethyl aluminium (TMA) and ethylene glycol (EG). However, in such existing molecular layer deposition, the functional group including an organic precursor has been restricted to a hydroxyl group, a carboxyl group and their derivatives and the organic-inorganic hybrid thin film prepared accordingly has a problem such that it becomes unstable and decomposed upon standing in the air.
In order to prevent characteristic deterioration of electronic devices etc. due to oxygen or moisture, development of a superior passivation film is in progress. Currently, the passivation film has various forms including the single film based on inorganic materials such as SiO2, SiN and Al2O3, the multi-layered film prepared by alternately depositing inorganic materials, and the multi-layered film prepared by alternately depositing inorganic materials and organic materials. While ion beam deposition, electron beam deposition, plasma beam deposition and chemical vapour deposition have been used to form inorganic passivation films, such existing techniques have problems in that their deposition temperatures must be high and that coverage of a thin film was not excellent.
Thus the atomic layer deposition (ALD) method that enables the formation of a passivation film at low temperatures has been receiving much attention. ALD represents the ideal technology for preparing inorganic and metallic thin films in which a self-controlled reaction is used in an atomic unit to deposit a mono atomic layer and may be considered to be a deposition technique of a new concept that enables control of the thickness of a mono atomic layer. However, it has not achieved the desired performance yet because of the pin hole taking place during the process of passivation film formation.